Hourly Output Research Articles

Performance evaluation of using evacuated tubes solar collector, perforated fins, and pebbles in a solar still - experimental study and CO2 mitigation analysis.

The combination of various methods of increasing evaporation rate can highly impact the performance of solar desalination. This investigation aims to find the impact of using evacuated tubes solar collector, perforated fins, and pebbles on the performance enhancement of a solar still. Simultaneously six-evacuated-tube solar collector to raise the evaporation rate of the system, the perforated fins to increase the heat transfer surface between water and absorber, and the immersed pebbles stone in the water to keep the high water temperature at low solar radiation were considered. The hourly and cumulative distillate output (DO) values are presented separately for the daytime and nighttime to provide extensive insight. The results indicate that on a sample day from the six months of experiments, which was in February 2019, the time for DO peak shifts from 1 to 3 p.m. Moreover, the temperature values for MSS experience almost 43 ℃ jumps on the peak and almost 19 ℃ increase on average compared to CSS. Furthermore, the cumulative DO in the daytime reaches from 2.515 to 6.662 L, while during the nighttime, an increase from 0.057 to 0.872 L is observed. Additionally, during the six months, the average DO jumps from 2.88 to 7.03 L, which means a significant enhancement of 144.1%. Moreover, the costs per liter of MSS and CSS are 0.0051 and 0.0056 dollars per liter, respectively. The net amount of CO2 reduction of MSS was improved by about 2.44 times higher than CSS.

Clear-sky spectral radiance modeling under variable aerosol conditions

The distribution of diffuse radiance over the sky hemisphere is an important quantity that is required in many applications. Its spectral variation is useful when considering processes having a spectral dependence, such as photovoltaics (PV). Here, a clear-sky spectral radiance model is developed from radiative transfer theory, using appropriate parameterizations to make the model suitable for rapid engineering-type calculations. The phase function of various aerosol mixtures combines three conventional Henyey-Greenstein functions. This procedure provides an effective solution to the problem of modeling the strong radiance within the circumsolar region, while being also accurate in low-energy areas of the clear sky. The dependence on wavelength of the coefficients of the simplified phase functions is efficiently described by polynomial ratios. The radiance is shown to vary from a relatively isotropic distribution in the UV to a very anisotropic one over the rest of the solar spectrum. The radiance model can be used to describe either ideal atmospheric situations or dynamic situations, for which the hourly outputs from the MERRA-2 reanalysis provide the optical properties of the aerosol mixture at any location. Examples of ideal radiance distributions include those corresponding to the reference spectra used for the performance characterization of PV cells. By integrating the modeled radiance over all wavelengths with appropriate weighting, both the broadband radiance and luminance can be derived. Although these two distributions are generally not identical, they are found sufficiently close, even under hazy conditions, to make them interchangeable in practice, within reasonable error limits. Compared to common empirical luminance distributions of the literature, the model appears more universal, because responsive to strong changes in aerosol composition.

Analyzing methods for calculating the output of the KSM-type surface miners at the Elga coal deposit

Introduction. The outlook is considered for blastless rock and coal mining at the Elga coal deposit when using continuous mining based on rotary conveyor lines and KSM-type cutting and loading machines. The article describes the mining and geological conditions of the Elga coal deposit. The article considers a range of sizes of the Sutterwhite-class rotary mining machines that contains seven models from the KSM (KRUPP Surface Miner) production series for open-pit mining with an output from 700 to 3000 m3 /h in a solid block or 1250–4000 m3 /h in soft ground. The article analyzes various methods for KSM-type surface miner output calculation for the conditions of the Elga coal deposit in the Republic of Sakha (Yakutia). Results and analysis. It has been established that the overburden at the deposit is strongly coherent, the machine’s output in terms of energy-power indicators ranges from 420 m3 for conglomerate and up to 850 m3 for siltstone, which is less than the rated technical output of KSM-2000R for solid rock equal to 1400 m3 /h. The results of the KSM-type surface miners output calculation by the kinematic factor show that at a rated layer height of 2.9 m, the output of the KSM-2000R was 1138 m3 /h, and the output of the KSM-2000RM was 1804 m3 /h. This correlation is maintained for different layer heights. KSM-2000RM has 80 buckets, while KSM-2000R has only 60 buckets, which explains different output. Additionally, the KSM2000RM depth of cut is 60 mm, which is greater compared to 47 mm of the KSM-2000R depth of cut. The Dombrovsky method for output calculation using the cross-section area of the cut and the bucket feed showed that the result obtained for the hourly output (1410 m3 /h) coincides with the hourly output of 1400 m3 /h specified in the technical passport for KSM-2000R. Conclusions. The results analysis showed that the highest output indicator of 1410 m3 /h for the KSM-2000R was obtained through the Dombrovsky method, and the output indicator of 1804 m3 /h for the KSM-2000RM was obtained through the calculation by the kinematic factor.

A new hybrid model for power forecasting of a wind farm using spatial–temporal correlations

This paper develops a new hybrid forecasting model for the hourly power output of multiple turbines (or plants), aimed at making use of both the spatial and temporal correlations of weather factors and power outputs from wind turbines (or plants). To account for the time-varying nature of local pattern and wind propagation, a new clustering algorithm named Kmeans–Hierarchical Clustering (KHC) is first used to adaptively cluster the wind turbines (or plants). Then, singular value decomposition (SVD) is employed to extract the leading components of the wind power of the wind turbines (or plants) in the same cluster. Finally, the support vector regression (SVR) models are built for the leading components and the predictions of the components are transformed into the predictions of the power output of each turbine (or plant) with the inverse SVD. The comparison results show that the proposed model is able to improve the forecast accuracy over the existing short-term forecasting models.

Mathematical Model of the Thermal Performance of Double-Pass Solar Collector for Solar Energy Application in Sierra Leone

The primary aim of this study was to utilize thermal energy for drying applications on March 21 (day of the year, n = 80) for the climatic weather conditions of Freetown, Sierra Leone. We evaluated the heat absorption of a double-pass solar air collector based on its configuration and exterior input variables before it was designed and mounted at the location of interest. This study considered a steady-state heat transfer using the thermal network procedure for thermodynamic modeling of a double-pass solar collector developed for drying and heating purposes. A mathematical model defining the thermophysical collector properties and many heat transfer coefficients is formed and numerically solved for this purpose. Indeed, this helped us generate the hourly temperature of different heat collector components, which aided in the performance evaluation of the system. The impact of the fluid flowing inside the collector on the temperature of the exit air was analyzed. It was observed that a flow rate of 0.02 kg/s produced an output of 91.72°C. The system's thermal efficiency improves with increased flow rate at various solar radiation intensities. It was observed that the thermal efficiency of the collector increases from 29% to 67% at flow rates of 0.01–0.3 kg/s. Collector lengths of 1.4 and 2.4 m are observed to be economically viable. An increase in the flow rate caused an increase on the efficiency. The hourly outputs for the collector components were represented graphically, and the curve patterns were similar to those of previous studies.

Analysis of carbon emission, carbon displacement and heterogeneity of Guangdong power industry

The marginal carbon emission factor can more accurately reflect the real-time carbon emission of the system. Based on the hourly output, load and external power data of Guangdong Province from 2017 to 2020, this paper uses the seemingly unrelated regressions (SUR) model to calculate the marginal carbon emission factor and carbon displacement coefficient of Guangdong’s power industry and compares them with the average carbon emission intensity, which can provide support for the formulation of emission reduction policies in the province. The study shows that the average carbon emission factor underestimates the actual carbon emission of the power system, and the marginal carbon emission factor is a more appropriate indicator to reflect the carbon emission of the system in policy regulation. In addition, this paper also analyzes the annual, quarterly and peak–valley heterogeneity of marginal carbon emissions. The results show that the marginal carbon emission factor at peak demand times increases significantly, featuring more gas turbines participating in power generation.

Renewable Energy Micro-Grid Interfacing: Economic and Environmental Issues

This paper presents a study on the technical, economic, and environmental aspects of renewable energy resources-based distributed generation units (DGs). These units are connected to the medium-voltage network to create a new structure called a microgrid (MG). Renewable energies, especially wind and solar, are the most important generation units among DGs. The stochastic behavior of renewable resources increases the need to find the optimum operation of the MG. The optimal operation of a typical MG aims to simultaneously minimize the operational costs and the accompanied emission pollutants over a daily scheduling horizon. Several renewable DGs are investigated in the MG, consisting of biomass generators (BGs), wind turbines (WTs), and photovoltaics (PV). For the proposed operating strategy of the MG, a recent equilibrium optimization (EO) technique is developed and is inspired by the mass balance models for a control volume that are used to estimate their dynamic and equilibrium states. The uncertainties of wind speed and solar irradiation are considered via the Weibull and Beta-probability density functions (PDF) with different states of mean and standard deviation for each hour, respectively. Based on the developed EO, the hourly output powers of the PV, WT, and BGs are optimized, as are the associated power factors of the BGs. The proposed MG operating strategy based on the developed EO is tested on the IEEE 33-bus system and the practical large-scale 141-bus system of AES-Venezuela in the metropolitan area of Caracas. The simulation results demonstrate the significant benefits of the optimal operation of a typical MG using the developed EO by minimizing the operational costs and emissions while preserving the penetration level of the DGs by 60%. Additionally, the voltage profile of the MG operation for each hour is highly enhanced where the minimum voltage at each hour is corrected within the permissible limit of [0.95–1.05] Pu. Moreover, the active power losses per hour are greatly reduced.

Impact of water depth on thermal efficiency, exergy efficiency, and exergy losses of finned acrylic solar still: an experimental study.

This paper presents a complete exergy analysis and exergy destruction of a finned acrylic solar still (SS) at 1, 2, and 3cm salt water depth (Wd). The coefficients of heat transfer of salt water-glass have been computed for evaporative, convective, and radiant heat transfer. Also, thermal efficiency, exergy loss of basin, saltwater, and glass was determined. The maximum hourly output of a finned acrylic SS at 1, 2, and 3cm Wd was1.23, 0.93, and 0.81kg, respectively. The daily yield of 5.67, 5.16, and 4.41kg was collected from the finned acrylic SS at 1, 2, and 3cm salt Wd, respectively. For the finned acrylic SS at 1cm Wd, the maximal exergy loss of the basin, saltwater, and glass was 604.3, 92.8, and 141.8W/m2, respectively. The thermal and exergy efficiency of the finned acrylic SS at 1cm Wd is 42.54 and 3.83%, respectively, while at 2cm salt Wd, it is 37.92 and 3.22% and for 3cm Wd is 31.2 and 2.7%. According to the findings, the exergy loss of saltwater in finned acrylic SS at 1cm Wd is minimal when compared to the exergy loss of saltwater in finned acrylic SS at 2 and 3cm Wd.

Energy and exergy analysis of conventional acrylic solar still with and without copper fins.

A detailed exergy analysis of a conventional and copper finned acrylic solar still has been presented in this manuscript. The evaporative, convective, and radiative heat transfer coefficient of water-glass has been calculated. Also energy efficiency, exergy destruction of basin, water, and glass has been determined. Conventional acrylic solar still with fins produced maximum hourly output of 1.24 kg and it produced daily output of 5.08 kg. The conventional acrylic solar still without fins produced maximum hourly output of 0.94 kg and it produced daily output of 3.75 kg. The maximum exergy destruction of the basin, water, and glass for the conventional acrylic solar still with fins are 655.206, 83.35, and 90.48 W/m2, respectively, and conventional acrylic solar still without fins are 616.28, 122.34, and 48.64 W/m2, respectively. The energy and exergy effectiveness of the conventional acrylic solar still with fins are 32 and 2.81%, respectively, and without fins are 24.93 and 1.69%, respectively. The study reveals that exergy destruction of water in the case of still with fins is minimum as related to the exergy destruction of water in the case of still without fins.

Research on economic benefits of “source, storage and load” in a multi-energy complementary combined cooling-heating-electricity system

In order to solve the randomness and volatility of new energy power generation, promote the local consumption of renewable energy, and maximize the economic efficiency of CCHP system, this paper combines the schedulable resources of energy production, energy storage and energy consumption into a “source storage” system, which can meet the demand of power supply, heating and cooling at the same time. The objective function is to minimize the daily operation cost of the cold heat electric hybrid energy system, and the power balance and equipment capacity of the system are constrained. Using the established mathematical model of the system framework, the particle swarm optimization algorithm is used to improve the CCHP programming model to obtain the adaptation curve and the hourly output of the optimal operation of the equipment with the maximum economic benefit. The operation and maintenance costs of the two modes are analyzed in depth. The results show that the optimization of “source storage and load” system not only improves the reliability of energy supply, but also reduces the cost of operation and maintenance and improves the economic benefits of the system.

Multi-objective operation optimization of regional integrated energy system based on NSGA-II algorithm

With the deepening of China’s energy market reform and the promotion of integrated energy services, the regional integrated energy system becomes an important development direction of energy supply system. In order to maximize the economic efficiency and reduce the air pollutant emission of the regional integrated energy system, the distributed power generation module and the cooling-heat-power (CCHP) triple-supply module are formed into a model, and the power balance, equipment capacity and environmental factors of the system are constrained with the objective function of minimizing the daily operation cost of the system as well as minimizing the air pollutant emission. Based on the mathematical system framework model and the optimal operation control strategy, the NSGA-II algorithm is used to solve the multi-objective programming model to obtain the Pareto solution set, and the hourly output of the optimal operation of the system equipment with both economic and environmental benefits is obtained. The results show that the daily operating costs and pollutant emissions of the district energy system are significantly reduced compared with those without optimization, which effectively solves the problems of low operating efficiency and serious environmental pollution of the district energy system and achieves the optimal operation with both economic and environmental benefits.

Theoretical and applied aspects of labour efficiency as a social and economic category

Introduction. Improving labour efficiency is the key to successful operation of any organization. Social and economic development of the state is largely depends on the in-depth study of labour efficiency management. These issues should be solved at certain enterprises at macro- and meso-economic levels.
 Aim and tasks. The purpose of the article is to deepen theoretical and methodological principles and develop practical recommendations for improving labour efficiency.
 Results. The generalization of theoretical and methodological provisions of the category of labour efficiency is carried out. Methodical approaches to the evaluation and measurement of labour efficiency at enterprises have been considered. It is established that labour efficiency, as an economic category, takes into account many aspects that reveal it through certain characteristics, which are expressed in labour productivity, quality and labour performance. It was found that increasing the production of surplus products can increase productivity, but will reduce its efficiency. It is noted that labour efficiency is a dynamic indicator that reflects evaluation of changes in the sum of indicators of labour quality and productivity, life quality of all stakeholders involved in the working process and the use of its results. It is proposed to consider the category "labour efficiency" in terms of qualitative and quantitative criteria and substantiate the essence of labour efficiency, which reflects qualitative component in the form of products of specific consumer quality with value added and quantitative component in the form of manufactured products to the amount of labour spent on its production. The method of building a model for determining the coefficients of rating of the factors of enterprise development using the method of linearization of the model of labour efficiency is proposed.
 Conclusions. It is proposed to evaluate labour efficiency at the enterprise using a quantitative criterion which is the average hourly output of one employee, and a qualitative criterion which is the average hourly value added per employee. The increase in value added at the enterprise is achieved through the optimization of all production processes. The comparative complex analysis by means of the method of defining specific rating coefficients (SRC) of influence of development factors on labour efficiency at the machine-building enterprises is carried out. Proposals have been developed to evaluate optimal conditions for the development, stability and decline (bankruptcy) of machine-building enterprises.

Data center heated greenhouses, a matter for enhanced food self-sufficiency in sub-arctic regions

This paper examines the possibility of increasing Northern Sweden’s degree of self-sufficiency in food supply, at the 65th latitude, by using a data center as a heating source for greenhouse production. A dynamic building energy simulation software was used to compute both the hourly exhaust air output from a 1 MW data center for one year and the corresponding heating demand for two different greenhouse sizes, 2000 m2 and 10 000 m2, and two different production scenarios. Partial year production, 1 Mars – 15 October, without grow lights and full-year production with grow lights. The study showed that 5.5–30.5% of the electrical input to a 1 MW data center could be recovered. The 2000 m2 greenhouse could operate almost entirely, 89.7–97.9%, on excess heat while only 50.0–61.5% of the 10 000 m2 greenhouse heating demand could be met for full- and partial-year production, respectively.Furthermore, it is concluded that the 10 000 m2 greenhouse with full year production was the most prominent case and would cost-effectively yield 7.6% of northern Sweden’s vegetable self-sufficiency.

Energy savings of block-scale facade greening for different urban forms

Many studies investigated the energy savings of buildings with green facades for different facade orientations and structures, whereas few studies have analyzed the influence of the urban form. This study evaluates the summer cooling energy savings of full-scale facade greening at blocks with different urban forms, using an integrated simulation with ENVI-met and EnergyPlus. Six idealized urban blocks (IUBs), each with two green-facade scenarios and one baseline bare-facade scenario, are established. The hourly output cooling loads of the bare- and green-facade scenarios are used to estimate the daily energy-saving rate (DER) and daily energy savings per m2 of green facades (DES). The results show that the block-scale facade greening provides a DER of 3.2–11% and a DES of 123–347 Wh/m2, representing a summer cooling energy reduction of 11–31 kWh for every m2 of the green facade. Among the six IUBs, the high-rise high-density site (HH) has the lowest DER and DES, and the mid-rise low-density site (ML) has the highest. A higher greening ratio (65%) results in a cumulative effect and a higher DER and DES than in the buildings with a lower greening ratio (35%). Shading provided by plants and substrates is the primary reason for the DES, whereas cooling and humidifying have relatively small influences, and a trade-off effect between the two is observed. The findings of this research can shed light on green-facade practices and building energy conservation in humid subtropical cities.

Probabilistic generation model for optimal allocation of wind DG in distribution systems with time varying load models

Renewable energy-based Distributed Generation (DG) is the most imperative part of modern power system and offers many potential benefits. To attain maximum benefits offered by DG integration, it is important to model the time varying characteristics of both load and generation. Therefore, this paper presents a new Weibull distribution-based time-coupled Probabilistic Generation model for optimal placement and sizing of wind DG with time varying voltage dependent (TVVD) loads. At first, Probabilistic model is proposed for wind speed uncertainty modeling to calculate the hourly output power from wind DG. Afterwards, the values of output power are considered for determining optimal allocation and penetration of wind DG in distribution network to minimize the Average Multi-Objective Index (AIMO) using Particle Swarm Optimization (PSO). The strength of the proposed methodology is validated on IEEE 33 and 69-bus systems. Results depict that, proposed methodology is appropriate for wind speed modeling and is suitable for implementing in power system planning. • Time-varying characteristics of load and generation are assumed for DG allocation. • Weibull distribution-based PG model is proposed to determine hourly wind DG output. • Hourly output power values are considered for the optimal allocation of DG. • The penetration level of wind DG is calculated for different TVVD load models.

Lightning attachment procedure optimization algorithm for nonlinear non-convex short-term hydrothermal generation scheduling

Short-term hydrothermal scheduling (STHS) is considered an important problem in the field of power system economics. The solution of this problem gives the hourly output of power generation schedule of the available hydro and thermal power units, which leads to minimization of the total fuel cost of thermal units for a given period of a time. The optimal generation of STHS is considered as a complicated and nonlinear optimization problem with a set of equality and inequality constraints such as the valve point loading effect of thermal units, the power transmission loss and the load balance. This paper proposes lightning attachment procedure Optimization (LAPO) algorithm for solving the nonlinear non-convex STHS optimization problem in order to minimize the operating fuel cost of thermal units with satisfying the operating constraints of the system. The performance of LAPO algorithm is validated using three different test systems considering the valve point loading effects of thermal units and the power transmission losses. The obtained results prove the effectiveness and superiority of LAPO algorithm for solving the STHS problem compared with other well-known optimization techniques.

Comparison of two methods of calculating NO2 and PM10 transboundary pollution by CMAQ chemical transport model and the assessment of the non-linearity effect

The comparison of two methods in calculating transboundary concentrations of NO2 and PM10 using CMAQ chemical transport model is presented. The total mean annual concentrations for the pollutants were computed from the hourly outputs of the CMAQ model. The first method for calculating the transboundary concentrations is based on switching off the emissions from the studied country, while the remaining emissions are the same as in the full model run. The second method is based on running the model with the emissions from the studied country only. The resulting concentrations are then subtracted from the full model run concentrations. The result of this subtraction represents the transboundary air pollution together with pollution originating from the interaction of national and foreign sources. The pollution which cannot be attributed unambiguously to national or foreign sources is caused by the non-linear processes included in the model. It is evaluated as the difference between the two methods. It is shown that the non-linearity effect is more expressed for PM10 than for NO2 annual mean concentrations. It is estimated that the non-linearity effect for PM10 can reach values up to 2.7 μg/m3 in absolute value, or up to 16% of the total annual mean concentrations and up to 25% of the total estimated transboundary concentrations in the studied area. It is also demonstrated that this non-linearity effect is more important for both pollutants during some episodes than in the annual mean. The method of removing the bias from the calculated transboundary concentrations is presented, together with the proposed method of evaluation of the uncertainties of the transboundary concentration calculations. The estimated transboundary contribution is evaluated at the locations of Slovak air-quality monitoring stations. The impact of several emission reduction levels on the estimation of the transboundary contribution is also presented. The simulations are performed for the reference year of 2015 for Slovakia, but the proposed methods can by applied universally.

Convective Transition Statistics over Tropical Oceans for Climate Model Diagnostics: GCM Evaluation

AbstractTo assess deep convective parameterizations in a variety of GCMs and examine the fast-time-scale convective transition, a set of statistics characterizing the pickup of precipitation as a function of column water vapor (CWV), PDFs and joint PDFs of CWV and precipitation, and the dependence of the moisture–precipitation relation on tropospheric temperature is evaluated using the hourly output of two versions of the GFDL Atmospheric Model, version 4 (AM4), NCAR CAM5 and superparameterized CAM (SPCAM). The 6-hourly output from the MJO Task Force (MJOTF)/GEWEX Atmospheric System Study (GASS) project is also analyzed. Contrasting statistics produced from individual models that primarily differ in representations of moist convection suggest that convective transition statistics can substantially distinguish differences in convective representation and its interaction with the large-scale flow, while models that differ only in spatial–temporal resolution, microphysics, or ocean–atmosphere coupling result in similar statistics. Most of the models simulate some version of the observed sharp increase in precipitation as CWV exceeds a critical value, as well as that convective onset occurs at higher CWV but at lower column RH as temperature increases. While some models quantitatively capture these observed features and associated probability distributions, considerable intermodel spread and departures from observations in various aspects of the precipitation–CWV relationship are noted. For instance, in many of the models, the transition from the low-CWV, nonprecipitating regime to the moist regime for CWV around and above critical is less abrupt than in observations. Additionally, some models overproduce drizzle at low CWV, and some require CWV higher than observed for strong precipitation. For many of the models, it is particularly challenging to simulate the probability distributions of CWV at high temperature.

Water solar distiller productivity enhancement using solar collector and phase change material (PCM)

This paper examines the use of a solar still associated with a solar collector, and phase change materials, in improving productivity in solar distillation. We contrasted productivity from a solar still associated with a solar collector both with and without PCMs, and explored relevant issues around design and installation. Experiments were conducted at an east–west orientation in Karbala at the end of October and beginning of November. Polyvinyl pyrrolidone (PVP K-30), polyethylene glycol (PEG 6000) and carboxymethyl cellulose sodium salt (CMC ), were used for their chemical properties as latent heat energy storage. The hourly output rose little where the solar distillation was coupled with solar collector but without LHTESS, through sunny days. There was an increase of about 30%–50% in freshwater output for LHTESS than was the case without. As daylight progressed the pure water created by the solar still increased. A solar still with solar collector for LHTESS is found to be increased according to the type of additive used. Water temperature was measured in a specified period. We studied the use of a solar still associated with solar collector both with and without PCM as thermal storage. The system run time was increased with the addition of PCM. System productivity and system efficiency also increased, by about 120 % and 40% respectively.

Increasing labor productivity as the major line of agricultural industry development

The improvement of the agricultural sector efficiency, a shift to innovative development approaches to increase the competitiveness of domestic agriculture in modern conditions is possible only if labor productivity increases. This task is more relevant today than ever, since the main factor of production – labor (labor resources) has a steady downward trend. The study has shown that in the agricultural sector of the region there is an increase of labor productivity both by value and volume. The application of deterministic factor analysis has revealed that in the dynamics both factors (number of employees and cost of production) had a positive impact on increasing labor productivity, but the increase in production volumes in the industry had a more noticeable effect (the value of the factor varied from 57.7 to 69.7 %). However due regard must be paid to the fact that agricultural production is subject to fluctuations and the decrease in the number of workers in the industry is sustainable. The positive impact and the main factor in the growth of annual labor productivity is an increase in the average hourly output of workers due to an increase in the yield and technical re-equipment, and this should be noted as a strategically important direction for the development of the industry. The normalization of employment also acts as a factor in further increasing labor productivity.